We will carry out a series of studies on the control of circulation and oxygen delivery of the fetus. We will quantify the roles of oxygen, carbon dioxide, acidosis, and arterior blood pressure in the control of blood flow to various regions of the fetal brain. In conjunction with these studies we will quantify the fetal brain electrical activity and its relation to cerebral blood flow, and blood gas values. We are developing a mathematical model of the fetal circulation and oxygen delivery using a systems analysis approach. In addition, we will quantify the relation of fetal and placental growth and placenta diffusing capacity to inspired oxygen concentration. We will quantify the relation of fetal oxygen levels to placental diffusing capacity, and the relation of fetal oxygenation to severity of maternal exercise.